The present invention relates to the field of locomotive tenders and specifically to such tenders which also incorporate drive axles powered by the attending locomotive(s).
A recent change in locomotive design has enabled a new approach to long haul train operations. This approach provides new benefits by leveraging this change and addresses an age old problem. The enabling change is the switch from DC to AC power in locomotives. This resulted in increased efficiency with the result that the locomotives can now generate more power than they are able to make use of with a normal configuration of drive axles.
One approach to this surplus has been to increase the number of drive axles available by adding a third truck in the middle of the locomotive. See U.S. Pat. No. 4,231,296 to Jackson. This approach is complicated by the need for the middle truck to offset laterally as the locomotive transits a curve. It also requires a redesign of the locomotive and would then replace existing locomotives.
In switchyard applications a xe2x80x9cslugxe2x80x9d unit, or xe2x80x9ccow and calfxe2x80x9d arrangement has been used. The slug is a converted locomotive which has drive axles but no engine or generator. The electrical power for the slug is drawn from the attending engine. Ballast, usually concrete, replaces the engine to provide sufficient weight for traction. Traction sand hoppers spread sand for increased traction effort as on a traditional engine. In at least one application, the belly fuel tank was left on the slug and hose run to the locomotive to allow it to use the fuel from the slug. The slug is controllable from the lead locomotive as in conventional MU operations. This arrangement is most applicable to heavy hump yard switching service where the engine is frequently moving strings of cars from a standstill and up an incline (the hump) at low speeds.
The age old problem is that of not being able to carry enough fuel in the locomotive to make non-stop long haul trips. In addition to fuel, the locomotive must also be periodically re-supplied with lubricating oil, water, and traction sand. Lacking the necessary range, trains must make mid-trip fueling stops to re-supply. In a typical situation, the train will stop at a fixed fueling stop which is maintained for that purpose. The locomotive is uncoupled from the train and moved to a roundhouse or servicing area where it is fueled, serviced, and the oil, water and sand re-filled. It may take as much as 12 hours per stop to uncouple the locomotive, route it through the switchyard to the service area, route it back to the train, and recouple it. That is a significant loss of time for a trip which requires about 60 hours of time under way.
The necessity to maintain the fixed fueling stops is also a significant expense. The facilities themselves must be maintained. Personnel must be employed to run the fueling stop and perform the service and fueling. Fuel and other consumables must be purchased and stored. Fuel prices vary widely across the country. Because of the logistics enforced by the range of the locomotives, it may be necessary to maintain a fixed fueling stop in an area where fuel prices are much higher than elsewhere along the route. This means that either fuel must be purchased at the local rates or purchased elsewhere and transported in at additional expense.
At least one railway company, Union Pacific, has tested the concept of providing additional fuel for the locomotives. A conventional tank car was converted to allow locomotives to draw fuel from the tank car while the train was underway. MU cabling was added to enable the locomotives to communicate as usual with the tank car positioned between them. The tank car itself did not utilize the MU signals. Running boards and handrails were removed as part of the modification, preventing the train crew from walking between the locomotives while the train was underway. No other consumables, such as lubrication oil, water or sand, was carried by the tank car. The modified tank cars, four total, were used for a short term test spanning a few months. While the concept was considered viable, the tank cars are no longer in use. A major drawback to this approach is the structural weakness of the tank car. It was not designed to become part of a locomotive consist where it is placed between two locomotives and subject to the stresses of locomotives under full power. Additional problems, such as the lack of walkways also restricted the utility.
There is a need for a supplemental unit which can serve a multi-part role in a locomotive consist. It should draw from the surplus power generated by the locomotives to supply additional tractive force via drive axles. Dynamic braking should also be available to assist in decelerating the train. The unit should carry sufficient additional fuel, lubrication oil, water, and sand to allow extended long haul trips to be made without stopping. It must also be able to transfer these materials to the locomotives on command while the train is underway. The design of the unit should be such that it fits seamlessly into a consist: standard MU cabling and command response; structural strength equivalent to a locomotive; walkways and handrails for crew movement; and symmetric coupling to allow connection to locomotives at both ends. Preferably this unit would work as a supplement to existing locomotives, requiring minimal locomotive modification, to protect the investment in the existing fleet.
The present invention is directed to an auxiliary drive tender which provides storage for fuel and other consumables, such as oil, sand and water, as well as traction motors and drive axles which supply both tractive force and dynamic braking.
According to the invention there is provided an auxiliary drive tender which has a frame and drive axles similar to a conventional locomotive while also storing a large quantity of fuel. The drive axles are powered by electricity from the locomotive and the fuel can be transferred to the locomotive while under way.
According to an aspect of the invention the auxiliary drive tender will also store and supply lubrication oil, water, and sand.
According to another aspect of the invention the traction motors also provide dynamic braking.
Further in accordance with the invention the traction motors, dynamic braking, fuel transfer, oil transfer, water transfer and sand transfer are all controlled from the lead locomotive via commands transmitted to the tender.
Still further in accordance with the invention, the auxiliary drive tender includes a power distribution circuit which connects to generators on two locomotives and distributes the power to the traction motors of the tender according to any of the following schemes: either locomotive generator may power all traction motors; each locomotive generator powers one set of traction motors for one truck; or the power of both locomotive generators is distributed to all traction motors.
The advantages of such an apparatus are that sufficient consumable supplies (fuel, oil, water, sand) are stored and transferred to the locomotive(s) while underway making it unnecessary to stop during a typical long haul trip. The traction motors and drive axles supplement both the tractive force available for moving the train and the dynamic braking force available for slowing the train. The design of the auxiliary drive tender is such that it fits into a conventional locomotive consist much like a conventional B-unit, simplifying train crew operations.
The above and other features and advantages of the present invention will become more clear from the detailed description of a specific illustrative embodiment thereof, presented below in conjunction with the accompanying drawings.